Hair dryers include air inlets drawing air in for use in drying; and there is a tendency for the air inlets to suck in bits of hair and other particles. To avoid it reaching the fan and the heating element, and to avoid the user's hair getting sucked into the fan, a filter is usually placed in the air inlet. This filter can become covered with bits of hair or other particles and, so, block the flow of incoming air. This can cause dangerous overheating of the heating element in the dryer and of the remaining air flowing out of the unit.
My invention gives a signal to the user whenever this clogging occurs.